Firefighters today were still at the scene of a blaze which ripped through a Birmingham city centre club early yesterday.

More than 500 people were led to safety by staff at Edward's No8 at 1.10am after revellers spotted smoke coming from a men's toilet on the third floor. Clubbers who returned to the scene yesterday, to see what had happened to the venue in Lower Severn Street, said there had been suggestions the blaze was started by someone setting off a firework inside.

A West Midlands Fire service spokesman said arson had not been ruled out. He said: "Fire investigation teams have been at the scene all day.

"It is plausible this may have been started by a firework."

More than 70 firefighters from across the city were called to the scene; they will maintain a presence over the next day or so as there are fears parts of the building may collapse after the roof and third floor were destroyed. Structural engineers and a fire investigation team were at the scene yesterday inspecting the building, part of which dates back to the 19th century.

Sector Commander Phil Amado-Taylor said: "The weight of the water in the timbers and floors is making tackling this fire difficult. There is a worry more could collapse.

"I believe everyone in the club was evacuated very quickly by staff, but until this incident is over we can't say for sure."

Edward's No8 has three rooms and bars over three floors, which play different genres of music – mainly gothic, 80s, and rock.

Carol Newman, of Kidderminster, was at the club with friends when the fire broke out. The 36-year-old said: "We were in the bar on the top floor when the fire alarms went off and we could see smoke coming from the men's toilets.

"Later I heard it had been started by a firework.

Rabinder Bhachu, another witness who lives in a nearby apartment block, said he saw flames and smoke shooting through the club's roof.

He said: "I was woken by the noise of the fire engines, as well as the smell of smoke coming into my building.

"The club is between two streets, and there seemed to be flames coming from either side of the building.

"It did seem to be spreading."

Last night bosses at the Alexandra Theatre, located behind Edward's No8, in Suffolk Street, cancelled the scheduled show A Bostin' Brummie Night Out, claiming it was "the responsible thing to do".

Ian Sandy, the show's producer, said: "We arrived here about midday and Station Street was sealed off, which meant nobody could get into the NCP which is where most theatregoers park when they come to the Alex.

"After a long telephone discussion with the general manager Andrew Lister, it was decided the show should not go on but instead be rescheduled for some time in the New Year.

"Box office staff have been frantically calling as many people as possible to let them know what was happening, because we were expecting about 400 people to see Carl Chinn, Ed Doolan and Malcolm Stent."

Lower Severn Street, Station Street and part of John Bright Street will remain closed today as investigations continue.